Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$61.47	8.229%	$66.5284	$66.53	$66.55	$66.50
Purchase #2	$121.63	13.523%	$138.078	$138.08	$138.10	$138.10
Purchase #3	$241.52	8.611%	$262.3173	$262.32	$262.30	$262.30
Purchase #4	$247.30	7.230%	$265.1798	$265.18	$265.20	$265.20
Purchase #5	$162.27	5.467%	$171.1413	$171.14	$171.15	$171.10
Purchase #6	$147.59	6.328%	$156.9295	$156.93	$156.95	$156.90
Purchase #7	$54.53	9.161%	$59.5255	$59.53	$59.55	$59.50
7 purchase totals =	$1,036.31		$1,119.6998	$1,119.71	$1,119.80	$1,119.60